Device for measurement of the torsional angular deviation of a loaded rotating or static shaft

Abstract

A torsional angular deviation measuring device comprising a first diffraction grating which is placed at one end of a shaft and a second diffraction grating placed at the other end or at least some distance from the first end. A beam of light from a light source is then passed through the first diffraction grating generating zeroth order and other order beams. The beams are thence passed through collimating optics and then through the second diffraction grating. The beams from the second diffraction grating are sensed by split photodiodes and the amount of angular deviation is then measured by comparing the phases of pulse trains generated from the different photodiodes with one another.

What is claimed: 
     
       1. Apparatus for measuring torsional angular deviation of a member subject to torsional forces comprising first and second diffraction means mounted in spaced apart relationship to said member, a source of light, light from said source being diffracted into a first plurality of zeroth and higher order beams by said first diffraction means, the zeroth and at least one higher order beam of said first plurality of order beams being further diffracted by said second diffraction means into a second plurality of order beams, the relative positions of at least two of the order beams of said second plurality of order beams providing a measure of the torsional angular deviation of said member. 
     
     
       2. The invention of claim 1 further comprising collimating means located between said first and second diffraction means for parallelizing at least two order beams of said first plurality of order beams before further diffraction by said second diffraction means. 
     
     
       3. The invention of claim 2 further comprising first and second detectors for detecting the positions of said at least two order beams of said second plurality of order beams and producing detector output signals in response thereto, and circuit means connected to said detectors for receiving said detector output signals and producing in response thereto a signal indicative of the torsional angular deviation of said member between said first and second diffraction means. 
     
     
       4. The invention of claim 1 further comprising detection means for detecting the relative positions of said at least two order beams of said second plurality of order beams and providing an output signal representative of the torsional angular deviation of said member. 
     
     
       5. The invention of claim 1 further comprising first and second detectors for detecting the positions of said at least two order beams of said second plurality of order beams and producing detector output signals in response thereto, and circuit means connected to said detectors for receiving said detector output signals and producing in response thereto a signal indicative of the torsional angular deviation of said member between said first and second diffraction means. 
     
     
       6. Apparatus for measuring torsional angular deviation of a member comprising: a source of light;   first diffraction means mounted to said member for diffracting light from said source into a plurality of order beams;   collimating means for rendering parallel at least two of said plurality of order beams from said first diffraction means;   second diffraction means mounted to said member in spaced relationship to said first diffraction means for receiving said parallel beams from said collimating means and diffracting said parallel beams into a second plurality of order beams;   first detector means for detecting a first one of said second plurality of order beams at a first diffraction angle with respect to said second diffraction means and producing a first detector signal in response thereto;   second detector means for detecting a second one of said second plurality of order beams at a second diffraction angle with respect to said second diffraction means and producing a second detector signal in response thereto;   means coupled to said first and second detector means for receiving said first and second detector signals and producing a signal indicative of the torsional angular deviation of said member between said first diffraction means and said second diffraction means.   
     
     
       7. A method for measuring the torsional angular deviation of a member comprising the steps of: (a) directing a source of light upon a first diffraction means mounted to a member subject to torsional forces to produce a first plurality of order beams;   (b) collimating at least two order beams of said first plurality of order beams;   (c) directing at least two collimated order beams of said first plurality of order beams upon a second diffraction means mounted to said member in spaced relationship to said first diffraction means to produce a second plurality of order beams;   (d) detecting the relative positions of at least two of the order beams of said second plurality of order beams to thereby provide a measure of the torsional angular deviation of said member between the first and second diffraction means.   
     
     
       8. The method of claim 7 wherein the step of detecting the positions of said at least two of the order beams of said second plurality of order beams comprises detecting the same with photoelectric detectors to produce detector output signals in response to said positions; and further comprising the step of processing said detector output signals to produce a signal indicative of the torsional angular deviation of said member.